1. Field of the Invention
This invention relates to a resist recycling apparatus and a method for recycling the same, and more particularly, this invention relates to a process for recycling resist wastes generated by a process for coating a resist on a substrate.
This application is a counterpart of Japanese application Serial Number 278589/1999, filed Sep. 30, 1999, the subject matter of which is incorporated herein by reference.
2. Description of the Related Art
A photolithography technique is generally used in the manufacturing of a semiconductor device.
Spin coating is generally used to form resist thin films on a semiconductor substrate. In a typical spin coating, liquid resist is dropped on to a silicon wafer by a nozzle. Spinning of the wafer spreads the resist over the wafer. After spinning, only a thin film of the resist is left on the surface of the wafer.
In excess of 95% of the resist is wasted in spin coating. Therefore, a lot of resist recycling techniques have been proposed, such as Japanese laid open number HEI 8-203804 and so on.
These prior arts cannot control the viscosity of the resist sufficiently to reuse recycled resist in the manufacturing of a semiconductor device.
An object of the present invention is to provide a resist recycling apparatus and a method for recycling a resist.
According to one aspect of the present invention, for achieving the above object, there is provided a resist recycling apparatus, comprising a viscosity control tank being supplied with wasted resist liquid, a solvent tank supplying a solvent to the viscosity control tank, a viscometer measuring s viscosity of the resist in the viscosity control tank, a control portion calculating the resin density of the resist according to the viscosity measured by the viscometer and the temperature of the resist, determining an amount of solvent to supply to the viscosity control tank according to the difference between the calculated resin density and a predetermined resin density, and a filter removing dust from the resist.
According to another aspect of the present invention, for achieving the above object, there is provided a method for recycling a resist comprising supplying waste resist to a viscosity control tank, measuring the viscosity of the resist in the viscosity control tank, calculating the resin density according to the measured viscosity and the temperature of the resist in the viscosity control tank, determining the amount of solvent to add to the resist according to the difference between the calculated resin density and the predetermined resin density, supplying a solvent to the viscosity control tank, and removing dust from the resist.